The present invention relates to a stroke determination system for a four stroke cycle engine, particularly to a stroke determination system for a four stroke cycle engine which is suitable for determining the stroke of a multi-cylinder V-type engine having ignition timings at irregular intervals.
In a four stroke cycle engine adopting an electronic fuel injector, determination of the stroke has been carried out based on both the phase of a camshaft of the engine and the phase of a crankshaft. On the other hand, Japanese Patent Laid-open No. Hei 10-227252 proposes a stroke determination system in which the phase of the camshaft is not detected. The intake pressure detected this time in a specified phase of the crankshaft is compared with the intake pressure detected one period before, and determination of the stroke and determination of the cylinder are conducted according to the magnitude relationship between the two intake pressures. By this system, the need to dispose a sensor for detecting the phase of the camshaft, in the cylinder head of the engine, is eliminated, and it is made possible to achieve reductions in the size and weight of the engine.
In the above-mentioned related art, determination of the stroke and determination of the cylinder are performed based on the subtle magnitude relationship between the two values of intake pressure. In this case, the intake pressure depends not only on the stroke of the engine but also on the running condition, i.e., whether the present condition is an accelerating condition or not, or whether the present condition is a decelerating condition or not. Therefore, there has been the technical problem that, where it is intended to discriminate the stroke and the cylinder on the basis of only the intake pressure irrespectively of the running condition, a confirmation work by carrying out a multiplicity of actual machine tests is needed, leading to an increase in the number of development steps.
Further, there is also the technical problem that, where it is intended to compensate an actually measured value of intake pressure for a value in a standard condition on the basis of a lot of data obtained through actual machine tests, the arithmetic load on an ECU is increased.